Egyptian security forces stand by their personnel carriers ahead of a military operation in the northern Sinai peninsula on Aug. 8, 2012. Egypt, which launched air raids against Islamist militants in Sinai for the first time in decades, faces a tough enemy that has used the peninsula's rugged terrain to evade capture in the past. (Stringer/AFP/Getty Images)

CAIRO — Egypt showed new toughness Wednesday in confronting militants in the restive Sinai Peninsula, with the military launching overnight airstrikes and President Mohamed Morsi ordering a security shake-up.

The assault marked the first time Egyptian fighter planes have carried out strikes in the region since the end of the country’s war with Israel in 1973. They appear to have been carried out with the blessing of Israel, which has pushed Egypt to aggressively tackle the rise of extremism along its border.

The strikes on Egyptian soil came three days after armed militants in the Sinai killed 16 members of Egypt’s security ­forces, broke through the border into Israel and attempted to launch a separate attack there. Among security officials fired by Morsi on Wednesday were Egypt’s intelligence chief, Murad Mowafi, and the governor of North Sinai province, Abdel Wahab Mabrouk; the president also ordered his defense minister to relieve the head of the country’s military police, a spokesman said.

The steps signaled a clear, if belated, acknowledgment from Morsi, Egypt’s first Islamist president, that Islamist militants who have taken root in the Sinai pose a significant challenge to Egypt. But they also raised questions about whether Egypt’s U.S.-funded military is capable of addressing the threat from the extremists, who advocate self-governance under sharia, or Islamic law.

The use of warplanes by Egypt appeared to show the limitations of a military apparatus whose dependence on heavy tanks and fighter aircraft reflect an orientation more toward land warfare than a counterinsurgency campaign.

(Gene Thorp/The Washington Post)

“The Egyptian army is well-equipped,’’ said Zeinab Abul-Magd, a history professor at the American University in Cairo and Oberlin College in Ohio who has studied the Egyptian military. “They have tanks and planes to crush these terror groups. But they have not trained their officers or soldiers to deal with the problems of Sinai.”

Egyptian state television reported Wednesday that overnight bomb strikes, carried out in response to a fresh wave of attacks on checkpoints, had killed at least 20 suspected militants. Sinai residents disputed that account in interviews, saying the offensive appeared to have been merely a show of force and a publicity stunt, and it remained unclear Wednesday whether the airstrikes involved bombs or missiles.

The deployment of troops and use of force in the Sinai is governed by a U.S.-brokered peace treaty between Egypt and Israel that has been in effect since 1979. A senior Israeli official declined to say whether Israel had been asked to sign off on the strikes, but cited “ongoing contacts’’ between the two countries.

Robert Springboard, an expert on the Egyptian military at the Naval Postgraduate School in California, said the country’s armed forces have never been eager to take on extremist cells operating in the Sinai. When militant groups carried out bombings in the 1990s and the past decade, Egypt’s intelligence service and Interior Ministry took the lead in the fight against them.

“The position taken by the military was, ‘This is really not our job,’ ” Springboard said in a phone interview.

Much of the Sinai has descended into lawlessness since Egypt’s wintertime revolt in 2011, as police stations in the Sinai were looted and Bedouin tribes and militants began to stockpile weapons streaming in from Libya. For now, Islamic courts are the preferred forum for settling disputes, and security forces seldom stray from the main highway. The area has the potential to become a powder keg, with some jihadists vowing to beat back any attempt by security forces to assert control there.

Morsi is under heavy pressure to endorse a crushing crackdown on militants in the region, but any missteps or abuses could trigger a backlash from Islamists, his main political base. At the same time, he faces resistance from top generals over the extent of his powers, and it was not clear Wednesday whether the military had signed off on the ouster of security officials.

On Tuesday, Morsi stayed away from the military funeral for the 16 slain soldiers — a conspicuous absence for a leader whose thorny relationship with the military is being closely watched. Angry Egyptians heckled and tried to assault Prime Minister Hesham Kandil when he arrived for prayers before the funeral, prompting his security detail to whisk him out.

The United States, which has given the Egyptian military more than $35 billion in the past three decades, has pressed the generals in Cairo to shift their focus to asymmetric threats, such as insurgencies, rather than plan primarily for a conventional war. U.S. officials made that case in a January 2010 meeting with senior Egyptian officials but encountered resistance, according to a cable written by then-U.S. Ambassador Margaret Scobey that was published by the WikiLeaks whistleblowing Web site.

No group has claimed responsibility for Sunday’s attack, in which a band of gunmen commandeered armored Egyptian military vehicles after killing the soldiers at an Egyptian checkpoint and used the vehicles to ram an Israeli border crossing. The attempted infiltration was thwarted by an Israeli airstrike.

After Egypt launched its own overnight strikes early Wednesday, Ibrahim el-Meneey, a tribal leader in the Sinai who acknowledges the presence of extremist militant cells in the area, said community leaders saw no evidence of fatalities. The only visible damage, he said, was a charred Toyota that he described as unoccupied when it came under fire.

Ahmad Abu Deraa, a local journalist, said he followed Egyptian ground troops to the sites of the strikes early Wednesday but saw no evidence of casualties.

Mona Zamalot, an activist based in the nearby city of al-Arish, said residents there and other densely populated areas in the Sinai are worried that the gunmen will leave the wilderness and seek refuge in those relatively urban areas if the crackdown intensifies.

“If the militants stay in the desert and mountains, they will fall,” she said. “They want to go into the cities.”